A pneumatic actuator for an active hood having a cylinder and a piston is known from DE 10 2006 008 900 A1, in which the piston is movable in the cylinder between a lower terminal position, in which the volume of a chamber delimited by piston and cylinder, which may be impinged by compressed gas, is minimal, and an upper terminal position, in which the volume of the chamber is maximal. The piston is lockable in the lower terminal position by an elongate detent body, in that it simultaneously engages in holes of the piston and the cylinder extending transversely to the movement direction of the piston.
A front face of the detent body is subjected to compressed gas flowing in from a pyrotechnic gas generator, to be displaced by it out of the hole of the piston and thus unlock the piston before the compressed gas reaches the chamber.
One problem of this known actuator is the difficulty of combining a sufficient mobility of the detent body with good security against premature penetration of the compressed gas into the chamber. Specifically, if compressed gas enters the chamber before the detent body is withdrawn from the hole of the piston, the compressed gas increases the friction acting between detent body and piston, so that the detent body may jam in the hole of the piston. The piston is then not unlocked and the hood is not raised. To ensure reliable unlocking of this known actuator, a high manufacturing precision is thus necessary.
At least one object of the present invention is to provide a pneumatic actuator for an active hood which ensures reliable unlocking of the piston even without high demands on the manufacturing precision. In addition, other objects, desirable features, and characteristics will become apparent from the subsequent summary and detailed description, and the appended claims, taken in conjunction with the accompanying drawings and this background.